The present invention relates to devices for lifting boats or personal watercraft. More specifically, the present invention relates to a hydraulicly operated platform that may be secured to a boat or a structure. Further still, the present invention improves upon available boat lifts by providing a boat lift that is capable of raising and lowering the platform in a substantially horizontal manner.
Boat lifts have long been available for use with large luxury watercraft such as personal yachts where boat lifts are utilized to raise and lower a smaller boat or dinghy that could be used to transport people to and from shore where the yacht had to be anchored offshore. With the increased popularity of personal watercraft such as JetSkis(copyright) or Waverunners(copyright) there is an increased need for a boat lift that is capable of raising and lowering these personal watercraft in and out of the water. Although there are many boat lifts available, many have substantial shortcomings or are too large to be attached to a pleasure craft such as a yacht or a house boat. Further still, many of the boat lifts were designed to raise and lower small inflatable boats or dinghies where weight distribution is not an important consideration.
Many of the presently available boat lifts utilize at least one hydraulic cylinder, or more likely two hydraulic cylinders operating in tandem to raise and lower the platform. Although, the two hydraulic cylinders are capable of providing the forces necessary to raise and lower the platform, many times the platform is not sufficiently rigid. Thus, when a personal watercraft is disposed upon the platform and the hydraulic cylinders are activated to lift the platform, many times the platform will lift at an angle due to the unbalanced weight disposed on the platform. This unbalanced condition makes it difficult for a person to stand on the platform because the unbalanced condition makes it unsafe.
As described above, many of the lifting devices available on the market utilize a platform and two hydraulic cylinders, where the hydraulic cylinders are connected to the platform. A problem associated with this type of layout is that the two hydraulic cylinders are only coupled together through the platform. In use, if the load placed on the platform is not equally balanced, one cylinder will lift the platform faster than the other cylinder. Therefore, as the platform ascends or descends it does so tipped at an angle. This tipping creates a dangerous situation because the boat or personal watercraft disposed upon the platform may slide off of the platform and cause injury to someone located nearby. Additionally, this tipping condition makes it difficult for a person to stand on the platform when the platform is being raised or lowered and may cause the platform to drag in the water when in a raised position. Further still, this tipping condition may not allow a locking mechanism to be activated, thus requiring additional steps to lock the platform into a safe position.
In addition to providing a lifting platform for a personal watercraft or boat, many times the boat lifting platforms may be utilized as a recreational device, such as a swimming platform, or a means for entry into the boat to which the platform is attached. Further still, many platforms include a support device for cradling a small boat or personal watercraft, these cradles are sometimes fixedly attached to the platform, thus making it difficult to use the platform for recreational purposes. Thus, it is desirable to provide a platform that is sufficiently rigid to be utilized as a swimming platform.
Furthermore, it is desirable to provide an improved lifting platform that is capable of providing a stable lifting platform for a personal watercraft or boat in addition to providing easier egress and departure to/from the boat or structure to which the lifting platform is attached.
In accordance with the present invention there is provided a lifting device for a boat, the lifting device includes a first platform and a plurality of linkage members, the plurality of linkage members configured to form at least two four-bar linkage assemblies, each four-bar linkage assembly having a first end pivotally attached to the first platform and a second end pivotally attached to a boat and at least one load sharing member configured to span and connect to at least two of the four-bar linkages together so that in use forces exerted by a hydraulic cylinder on the four-bar linkage is shared equally. The lifting device further includes at least one hydraulic cylinder, the cylinder having a first end and second end, the first end being pivotally connectable to the structure of a boat and the second end pivotally attached to at least one linkage member, and a fluid device in communication with the hydraulic cylinder.
In accordance with another aspect in accordance with the present invention there is provided a lifting device for lifting a personal watercraft or boat, the lifting device includes a first platform and a plurality of linkage members, the plurality of linkage members configured to form at least two four-bar linkage assemblies, each four-bar linkage having a first end pivotally attached to the platform and a second end pivotally attached to a boat. At least two force applying devices configured to raise and lower the two four-bar linkage assemblies, each force applying device having a first end and second end, the first end being pivotally connectable to the structure of a boat and the second end pivotally attached to at least one linkage member. The lifting device further includes a second platform, the second platform pivotally connected to the two four-bar linkage assemblies, and a control device in communication with the two force applying devices, the control device configured to control the motion of the each of the two force applying devices.
In accordance with yet another aspect of the present invention there is provided a lifting device for lifting a personal watercraft or boat, the lifting device includes a first platform and a second platform, a plurality of linkage members being pivotally connected to the first and second platforms. At least one force applying device configured to raise and lower the first and second platforms, the force applying device having a first end and second end, the first end being pivotally connectable to a boat and the second end pivotally connected to at least one linkage member, and a control device in communication with the force applying device, the control device configured to control the motion of the force applying device, whereby the force applying device and control device are configured to move both the first platform and the second platform from a raised position to a lowered position, wherein when the second platform is moved from a raised position to a lowered position, the second platform is moved less than half a distance the first platform is moved from the raised position to the lowered position.